Diisopropylphenyl-imidazole (DII): A new compound that exerts anthelmintic activity through novel molecular mechanisms

Abstract

Nematode parasites cause substantial morbidity to billions of people and considerable losses in livestock and food crops. The repertoire of effective anthelmintic compounds for treating these parasitoses is very limited, as drug development has been delayed for decades. Moreover, resistance has become a global concern in livestock parasites and is an emerging issue for human helminthiasis. Therefore, anthelmintics with novel mechanisms of action are urgently needed. Taking advantage of Caenorhabditis elegans as an established model system, we here screened the nematicidal potential of novel imidazolium and imidazole derivatives. One of these derivatives, diisopropylphenyl-imidazole (DII), is lethal to C. elegans at both mature and immature stages. This lethal effect appears to be specific because DII concentrations which prove to be toxic to C. elegans do not induce significant lethality on bacteria, Drosophila melanogaster, and HEK-293 cells. Our analysis of DII action on C. elegans mutant strains determined that, in the adult stage, null mutants of unc-29 are resistant to the drug. Muscle expression of this gene completely restores DII sensitivity. UNC-29 has been largely reported as an essential constituent of the levamisole-sensitive muscle nicotinic receptor (L-AChR). Nevertheless, null mutants in unc-63 and lev-8 (essential and non-essential subunits of L-AChRs, respectively) are as sensitive to DII as the wild-type strain. Therefore, our results suggest that DII effects on adult nematodes rely on a previously unidentified UNC-29-containing muscle AChR, different from the classical L-AChR. Interestingly, DII targets appear to be different between larvae and adults, as unc-29 null mutant larvae are sensitive to the drug. The existence of more than one target could delay resistance development. Its lethality on C. elegans, its harmlessness in non-nematode species and its novel and dual mechanism of action make DII a promising candidate compound for anthelmintic therapy.

Comparison of electrophysiological and motility assays to study anthelmintic effects in Caenorhabditis elegans

“…3 G). The calculated IC 50 value of 13.8 μM ( Table 1 ) for LEV-induced paralysis compared favorably with concentration response data of former studies ( Qian et al, 2008 ; Sloan et al, 2015 ; Ding et al, 2017 ; Blanco et al, 2018 ; Risi et al, 2019 ). For example, Qian et al (2008) reported an IC 50 value for LEV of 9 μM in their motility assays, while a PDMS-microfluidic chip approach reported a lower IC 50 value of 2.2 μM ( Ding et al, 2017 ).…”

Drug discovery: Insights from the invertebrate Caenorhabditis elegans

“…Using C. elegans mutant and transgenic strains, we found that DII effects on adult nematodes rely on a previously unidentified UNC‐29‐containing muscle AChR, different from the classical Levamisole‐sensitive AChR. Interestingly, DII targets appear to be different between larvae and adults as unc ‐ 29 null mutant larvae are sensitive to the drug 66 . Summing up, using the model C. elegans we demonstrated that DII fulfills the major criteria necessary for the development of a novel anthelmintic, namely phylogenetic specificity and a novel biochemical mode of action.…”

“…Although this method has contributed to the elucidation of MOAs for several compounds previously proven to be biologically active, 137,138 the agar‐based technique does not permit large scale screenings because it is labor‐ and time‐consuming and needs large quantities of drugs 14 . Even with limitations, these assays are still very valuable for assessing small compound libraries 66 …”

“…14 Even with limitations, these assays are still very valuable for assessing small compound libraries. 66 The introduction of C. elegans liquid cultures in multi-well format together with workflow automation from worm transfer to data analysis enabled the development of HTS assays. 139,140 Moreover, the breakthrough of microfluidic devices for C. elegans have improved the strength of HTS mainly thanks to the small amounts of compound (microscale) that are required and to the possibility of observing worms in parallel or in a serial manner.…”

“…78 Thus, while the presence of the imidazole ring appears to be important for bioactivity, it does not restrict the molecular targets where imidazole-containing anthelmintics can act. Recently, taking advantage of C. elegans as an established model for parasiticnematodes, we screened the nematicidal potential of novel imidazolium and imidazole derivatives 66. We identified a new compound, diisopropylphenyl-imidazole (DII), that is lethal to C. elegans through a novel mode of action that includes differential targeting in larvae and adult nematodes.…”